Multi-site campaign for transit timing variations of WASP-12 b: possible detection of a long-period signal of planetary origin

TL;DR

This study conducts a multi-site observational campaign of WASP-12 b to investigate transit timing variations, suggesting the possible presence of an additional long-period planetary companion based on refined data analysis.

Contribution

It provides new transit observations, refines system parameters, and proposes a two-planet model explaining timing variations better than a single-planet scenario.

Findings

Detected a potential periodic transit timing signal.

Supported the existence of a second planet through combined data analysis.

Indicated the proposed two-planet system is dynamically stable.

Abstract

The transiting planet WASP-12 b was identified as a potential target for transit timing studies because a departure from a linear ephemeris was reported in the literature. Such deviations could be caused by an additional planet in the system. We attempt to confirm the existence of claimed variations in transit timing and interpret its origin. We organised a multi-site campaign to observe transits by WASP-12 b in three observing seasons, using 0.5-2.6-metre telescopes. We obtained 61 transit light curves, many of them with sub-millimagnitude precision. The simultaneous analysis of the best-quality datasets allowed us to obtain refined system parameters, which agree with values reported in previous studies. The residuals versus a linear ephemeris reveal a possible periodic signal that may be approximated by a sinusoid with an amplitude of 0.00068+/-0.00013 d and period of 500+/-20 orbital periods of WASP-12 b. The joint analysis of timing data and published radial velocity measurements results in a two-planet model which better explains observations than single-planet scenarios. We hypothesize that WASP-12 b might be not the only planet in the system and there might be the additional 0.1 M_Jup body on a 3.6-d eccentric orbit. A dynamical analysis indicates that the proposed two-planet system is stable over long timescales.